The invention relates to an improved system for cooling a piston, and lubricating and cooling a connecting rod bushing and a piston pin contact surface.
Reciprocating piston internal combustion engines include one or more pistons that are reciprocally disposed within corresponding combustion cylinders. The pistons are interconnected with each other through the use of a rotatable crankshaft. Rotation of the crankshaft causes each piston to reciprocate within its corresponding combustion cylinder. Typically, each piston is pivotally connected to one end of a connecting rod by a piston pin. The connecting rod includes a bore defining a bearing that receives a piston pin of the piston such that the connecting rod pivots through a relatively small pivoting angle about the piston pin during reciprocation. The other end of the connecting rod is also pivotally coupled to the crankshaft which also pivots through a relatively small angle. Lubrication of the moving and pivoting parts within an internal combustion engine is essential during operation, as the lubricant eases friction between moving/pivoting parts and aids in the removal of heat. The lubricant generally used is oil. Two areas where it is desired to provide lubrication and/or cooling in the internal combustion engine is the piston pin and the crown of a piston.
It is known to indirectly supply a lubricant such as oil to the piston pin by splashing the oil proximate to the piston pin area. In one form, oil that is sprayed onto the piston undercrown area specifically for cooling the piston crown which then splashes onto the piston pin bore of the connecting rod. Since the piston pin bore of the connecting rod is disposed about the piston pin, the oil wicks into the piston pin bore of the connecting rod bearing area defined between the piston pin and the connecting rod bore to provide lubrication. While the splash method does supply lubricant to the piston pin area, the amount of lubricant supplied to the piston pin by the splash method may not be satisfactory. Further, the splash method is a passive rather than an active or positive method of providing lubrication and cooling to the piston pin and thus is not preferable.
It is also known to supply lubricant to the piston pin via a hole drilled longitudinally through a corresponding connecting rod. The connecting rod bore is in fluid communication with a lubricant supply via the crankshaft. In this manner, pressurized lubricant may be provided to the piston pin resulting in a positive method of lubrication. However, the structural integrity of the connecting rod is compromised by the oil hole drilling in the connecting rod itself. Alternatively, if the connecting rod is enlarged to compensate for the oil hole drilling, thereby preserving the structural integrity of the connecting rod, weight and size for example, then become of particular concern. Moreover, this design results in an undesirable increase in manufacturing costs. Additionally, this method is prone to unacceptable oil leakage from the bearing on the crankshaft. Thus, providing an oil hole drilling in the connecting rod for supplying lubricant to the piston pin is not preferable.
To enhance cooling, well known oil cups or traps have been used to trap the oil as it drains downwardly and thereafter cause additional splashing as the piston reciprocates. For example, U.S. Pat. No. 4,286,505 to Amdall discloses a two-piece oil cooled piston including an annular groove in an upper crown portion of the piston and a trough-like fluid trap formed on the lower portion of the piston opposite the annular groove. The trap is formed in part by a ledge extending axially upwardly and outwardly toward the upper crown portion. The trap includes a slot for permitting the pressurized stream of oil from a nozzle to be directed past the ledge into the groove. When the piston is at bottom dead center, the spray from the nozzle enters and cools the annular groove. When the piston is at top dead center, the spray from the nozzle cools a cooling dome toward the center of the piston. This momentary cooling is advantageous but does not continuously cool both the annular groove and the dome.
U.S. Pat. No. 4,377,967 discloses a two-piece piston assembly including a piston-oil retention cup attached beneath the undersurface of the piston crown to hold oil directed to the crown by a nozzle to enhance cooling of the crown. The cup includes a grommet to permit the pressurized oil to be delivered through the cup to the crown.
U.S. Pat. No. 5,595,145 discloses a cooling structure for a piston including an annular cooling cavity in the upper portion of the piston for receiving sprayed oil from a nozzle. A distributing member is formed within the cooling cavity on the top wall surface of the cooling cavity downstream of the entrance to the cavity for splitting the spray into two streams of predetermined proportions. The two streams are directed into the cooling cavity in opposite directions.
U.S. Pat. No. 5,065,707 discloses an engine cooling system including a piston having a skirt with guide ribs for distributing sprayed oil to the piston pin, an upper portion of the piston connected to the skirt and a space between the skirt and the upper portion. The guide ribs are formed on the skirt and extend radially inwardly and upwardly toward the upper portion of the piston. U.S. Pat. No. 4,895,111 discloses a similar arrangement.
It is, therefore, one object of the present invention to overcome the deficiencies of the prior art and to provide a simple piston cooling arrangement for an internal combustion engine which effectively cools the piston and cools/lubricates the piston pin/connecting rod connection.
Another object of the present invention is to provide a piston cooling system and piston which effectively cools the piston crown and lubricates/cools the piston pin area using a single cooling nozzle.
Yet another object of the present invention is to provide a piston cooling system which effectively cools the piston crown and lubricates/cools the piston pin while minimizing the cost and design complexity of the engine.
Still another object of the present invention is to provide a piston with a closed gallery which is capable of effectively deflecting a flow of oil to ensure cooling of the piston crown and lubrication/cooling of the piston pin.
These and other objects are achieved by providing an internal combustion engine, comprising an engine body including an engine cylinder and a piston positionable in the engine cylinder including an upper crown portion, at least one depending support portion and a skirt. The upper crown portion includes an under surface and a cooling oil gallery formed in the under surface. The engine also includes a connecting rod, a piston pin extending through the depending support portion to connect the connecting rod to the piston and a cooling nozzle mounted on the engine to direct oil along a flow path toward the cooling gallery. The engine further includes a deflecting surface extending from one of either the upper crown portion or the skirt wherein the deflecting surface is positioned in the flow path of oil from the cooling nozzle to deflect the portion of the oil into a path toward the piston pin while permitting another portion of the oil flowing along the flow path to flow to the piston cooling oil gallery. The invention is also directed solely to the piston for connection to the connecting rod via the piston pin wherein the piston is positionable in an engine for cooling by oil flowing along the flow path from the cooling nozzle. In either case, the skirt may be formed integrally with the upper crown portion and a piston may include a bottom wall at least partially covering the cooling oil gallery. The piston may further include an inlet flow port formed in the bottom wall and positioned to permit oil flowing along the flow path to enter the cooling oil gallery. The deflecting surface may be designed so that the portion of oil flowing along the flow path onward to the cooling oil gallery is not deflected and therefore flows through an undeflected flow path directly to the oil gallery. Also, the bottom wall may be in the form of a cover plate mounted on the upper crown portion. In this case, the deflecting surface may be formed on a baffle formed by a portion of the cover plate and including a distal edge positioned in the flow path. The deflecting surface may extend outwardly toward an outer periphery of the piston and downwardly away from the upper crown portion. The deflecting surface may also be formed on a baffle formed integrally with the upper crown portion wherein the baffle includes a distal edge positioned in the flow path. The deflecting surface may extend at a predetermined angle, and include a predetermined deflecting surface area relative to an inlet flow area of the inlet flow port, to optimize the amount of oil deflected and the amount permitted to enter the cooling gallery to thereby ensure proper cooling of the upper crown portion and proper cooling and lubricating of the piston pin and connecting rod.